From mboxrd@z Thu Jan  1 00:00:00 1970
From: kkonaka@mac.com
Subject: stack -> PROT_EXEC/why?
Date: Sun, 04 Aug 2002 21:22:33 -0400
Sender: linux-c-programming-owner@vger.kernel.org
Message-ID: <sqby9bmnlpi.wl@nue.mac.com>
Mime-Version: 1.0 (generated by SEMI 1.14.3 - "Ushinoya")
Return-path: <linux-c-programming-owner@vger.kernel.org>
List-Id: <linux-c-programming.vger.kernel.org>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: linux-c-programming@vger.kernel.org

hi,
casually looking at files like this:
glibc-2.2.3/linuxthreads/manager.c
 |       res_addr = mmap(map_addr, stacksize + guardsize,
 | 		      PROT_READ | PROT_WRITE | PROT_EXEC,
 | 		      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 it appears PROT_EXEC is also given to the per thread
stack(?) pages -- why is it the case?  that is - if we
consider things like buffer overflow (security)
problems, isn't it better not give PROT_EXEC unless
abslutely necessary? [so -- maybe there *is* some
absolute necessity I'm not aware of,... :(]
 (stepping back) is PROT_EXEC also given to ordinally
stack segment of single threaded programs? was there
any API to retrieve page protection bits given only
arbitrary VM addresses?
regards,
kenji